External Flow Analysis in SOLIDWORKS Flow Simulation

SOLIDWORKS add-on – Flow Simulation – allows you to simulate liquid and gas flows to calculate various characteristics: temperature, flow rate, pressure, etc. In this article, we will consider the case when a cylinder is in the path of the external flow of water. Let’s see how the balloon affects the speed, analyze the formation of flow vortices. Let us calculate the value of the resistance force that the balloon exerts on the flow, and to obtain more accurate results, we will use the function Mesh adaptation… And that is not all!

Introduction

We have an arbitrary container, which we placed in the stream of water (Fig. 1).

By adding Flow Simulation module into the SOLIDWORKS interface, create New project, where you can specify the configuration of the model, if any, and rename the project (Fig. 2).

Before continuing, let me remind you that if you prefer watching lessons over reading educational materials, welcome to our YouTube channel. “SOLIDWORKS School”… By link you will find a video where we learn to analyze flow with Flow Simulation.

Formulation of the problem

There are several ways to set task conditions. In our case, we will use the function Project Wizard… This function automatically creates a new project, allowing you to specify the name and configurations. We will leave the SI units by default, but change the Kelvin degrees to Celsius degrees (Fig. 3).

Next, we set the conditions for the type of problem (Fig. 4). First is the challenge External, that is, the stream flows around a solid body (balloon). Then we need to set the condition Nonstationarity, since we are considering a transient flow, that is, changing over time. The values Total time and Time step we leave it by default, we can clarify these parameters later. We will also select the condition Gravity – and be sure to check that the acceleration due to gravity is directed correctly.

The next step is to set the fluid (Fig. 5), in our case it is water. In the tab Liquids choose Water… Push the button Further and proceed to setting the conditions on the walls – we will leave these values by default.

And finally in the window Project Wizard we set the initial conditions of the problem (Fig. 6). Here we indicate only the flow velocity along the Z-axis in the opposite direction: 5 m / s. In the same window, you can set the speed using dependencies, table values or a formula.

Concerning Computational domain (that is, the one in which the calculations will be carried out), we set it arbitrarily: either by arrows on the model, or by specifying the coordinates of the area (Fig. 7).

Calculation options

Now, for our problem, let us establish the nonstationarity conditions. Right-click on the line Input data and choose Calculation control options (fig. 8). In the window that appears (Fig. 9), set the value Physical time, which pulled up here when we chose the parameter Nonstationarity in Project Wizard… This parameter means the time until which the calculation will be performed; set it to 5 seconds. In the same window, open the tab Payment and choose Time step – Manually, equal to 1 second.

Next, go to the tab Mesh adaptation (fig. 10). Adapting a grid means breaking up its cells so that their total number increases until a given resolution is reached. Flow Simulation automatically adapts during the calculation. Install maximum allowed number of cells: 7,500,000. For mesh adaptation strategies (it depends on this parameter at what moments of the calculation the mesh adaptation will be performed) choose Periodically and Physical time… Period we define equal to one second.

Global goal

We define Global goal, which will determine the strength of resistance. In our case, this is the force along the Z axis (Fig. 11). With the right mouse button we call Goals -> Add Global Goal and select the parameter Strength (Z)…

results

After the calculation is started and completed, we can view the results of our research in various versions. First, let’s build Sectional pictureby selecting the section plane From above, and as display types Fill (corresponds to pressure) and Vectors (corresponds to speed) – fig. 12.

On the diagram (Fig. 13) it is noticeable that the pressure is higher at the bottom – the weight of the water above affects. This takes into account a parameter known as pressure potential. From the vectors (arrows), we see how the flow enters the balloon at the bottom of the neck, and at the top it tries to leave it. Taking a look at the size of the arrows that show the flow rate, we note that they are shorter near the walls than elsewhere. The speed decreases due to wall friction.

Let’s create another Sectional pictureby setting the grid as the display type (Fig. 14). After plotting the plot, we see that the mesh is automatically refined in places of the swirling flow and where the flow rate differs significantly from the specified one.

Now let’s open in Results tab Objectives and see the value of the resistance force (Fig. 15). Negative values appear as a result of a mismatch between the direction of the force and the direction of the Z axis.

And finally, we will measure the pressure on the cylinder surface and its change over time. We open in Results window Surface parameters, select the edge of the balloon (Fig. 16) and set the parameter Pressure… In the same window, but on the tab Evolution in time select all moments in time and the team Show…

Output

Maxim Salimov, technical specialist in SOLIDWORKS CSoft Group E-mail: salimov.maksim@csoft.ru

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Want to learn more about calculations in SOLIDWORKS? Read our articles:

one. Thermal Analysis in SOLIDWORKS Simulation Using a Microchip as an Example

2. Simple Flow Simulation Calculation